Cooling System: Description and Operation

DESCRIPTION AND OPERATION






The cooling system includes:
1. A radiator, in which coolant flows through the radiator tubes and is cooled by air passing over the cooling fins assisted by the radiator electric motor and fan blade. Coolant is then circulated:
a. From the radiator outlet tank through the water pump.
b. Into the cylinder block.
c. Returns to the radiator to complete the circuit.
2. A water thermostat, which is located in a water outlet connection on the engine.
a. The water thermostat ensures rapid engine warm-up by restricting engine coolant flow at lower operating temperatures.
b. It also assists in keeping the engine operating temperature within predetermined limits.
3. A water pump, which has a conventional design and is driven by the drive belt.
4. A cooling fan motor which is activated by the Constant Control Relay Module (CCRM).
a. The cooling fan motor is mounted within a fan shroud behind the radiator.
b. The CCRM actuates the cooling fan motor when the coolant reaches a specified temperature, when the engine reaches a specified speed, or when the A/C clutch is activated, if equipped.

NOTE: With A/C ON, the radiator electric motor will run continuously. The radiator electric motor will not cycle ON and OFF with the A/C clutch.

NOTE: An exception to this is when vehicle speed is over 72 km/h (45 mph) and coolant temperature is below 104° C (220° F). The radiator electric motor will then automatically shut off.

5. A separate radiator coolant recovery reservoir located beside the radiator, which helps to maintain the correct volume of engine coolant. The coolant expands as the temperature and pressure rise in the system.
a. When the limiting system working pressure is reached, the pressure relief valve in the radiator cap is lifted from its seat.
1. This allows coolant to flow through the radiator filler neck and the radiator overflow hose into the radiator coolant recovery reservoir.
2. The radiator cap has a rubber seal on the underside to prevent leakage.
b. When the system temperature and pressure drop, the coolant contracts in volume and the pressure in the radiator is reduced.
1. The coolant in the radiator coolant recovery reservoir then flows back into the radiator through the vacuum relief valve in the radiator cap.

WARNING: Disconnect the cooling fan prior to performing any underhood service, since the fan blade could cycle if the ignition switch is left in the run position.

CAUTION: The addition of more water than recommended will raise the freezing protection temperature and weaken the corrosion inhibitors. Refer to Specifications for the cooling system capacity.

NOTE: The cooling system must be maintained with the correct concentration and type of anti-freeze to prevent corrosion damage.